Monday
February 8, 2016

# Posts by SARA

Total # Posts: 4,234

Chemistry
Ethane, C2H6, forms ·CH3 radicals at 700.°C in a first-order reaction, for which k = 1.98 h-1. (a) What is the half-life for the reaction? (b) Calculate the time needed for the amount of ethane to fall from 1.00 10-3 mol to 2.48 10-4 mol in a 500. mL reaction vessel...
June 28, 2013

Chemistry
When 0.13 g of H2 and 0.18 g of I2 are confined to a 150. mL reaction vessel and heated to 700. K, they react by a second-order process (first order in each reactant), with k = 0.063 L·mol-1s-1 in the rate law (for the rate of formation of HI). (a) What is the initial ...
June 28, 2013

Chemistry
Dinitrogen pentoxide, N2O5, decomposes by a first-order reaction. What is the initial rate of decomposition of N2O5 when 3.6 g of N2O5 is confined in a 0.77 L container and heated to 65°C? For this reaction, k = 5.2 x 10^-3 s-1 in the rate law (for the rate of ...
June 28, 2013

Chemistry
Dinitrogen pentoxide, N2O5, decomposes by first-order kinetics with a rate constant of 0.15 s-1 at 353 K. (a) What is the half-life (in seconds) for the decomposition of N2O5 at 353 K? (b) If [N2O5]0 = 0.0579 mol·L-1, what will be the concentration of N2O5 after 4.0 s...
June 28, 2013

Chemistry
a) 2A --> B + 2C b) A --> C + 2D
June 28, 2013

Chemistry
Determine the rate constant for each of the following second-order reactions. In each case, express your results in terms of the rate law for the loss of A. (a) 2 A B + 2 C, given that the concentration of A decreases from 2.74 mmol·L-1 to 1.46 mmol·L-1 in 122 s...
June 28, 2013

Chemistry
I understand, but what is K or how can I determine K?
June 28, 2013

Chemistry
I don't understand how to figure out K. I used the information in the problem given to solve for k, and then plug that k in to solve for t, but it's not the correct answer.
June 28, 2013

Chemistry
The half-life for the second-order reaction of a substance A is 58.2 s when A0 = 0.63 mol L-1 Calculate the time needed for the concentration of A to decrease to the following values. (a) one-third of its original value (b) one-sixth of its original value (c) one-seventh of ...
June 28, 2013

Chemistry
A total charge of 96.5 kC is passed through an electrolytic cell. Determine the quantity of substance produced in each of the following cases. (a) the mass (in grams) of silver metal from a silver nitrate solution (b) the volume (in liters at 273 K and 1.00 atm) of chlorine ...
June 21, 2013

Chemistry
Predict the standard emf of each of the following galvanic cells. (a) Sn(s)|Sn2+(aq)||Sn4+(aq),Sn2+(aq)|Pt(s) (b) Pt(s)|Fe3+(aq),Fe2+(aq)||Ag+(aq)|Ag(s) I don't want the answer, I want the procedure/methods of how to do these types of problems.
June 21, 2013

Chemistry
Balance the reaction of plumbate ions and hydrochlorite ions: Pb(OH)42-(aq) + ClO-(aq) → PbO2(s) + Cl- I put: Pb(OH)3-(aq) + ClO-(aq) → PbO2(s) + Cl-(aq) + H2O(l) + OH-(aq) It said: The reaction described in your answer is not balanced. One or more of your ...
June 21, 2013

Chemistry
Reaction of hydrazine with chlorate ions N2H4(g) + ClO3-(aq) → NO(g) + Cl-(aq) Balanced: 3N2H4(g) + 4ClO3-(aq) → 6NO(g) + 6H2O(l) + 4Cl-(aq) Reducing agent: ClO3- Oxidizing agent: N2H4 Right?
June 21, 2013

Chemistry
Either my online portal hates me, or I don't understand how to balance properly. QUESTION Balance reaction of arsenic(III) sulfide with nitric acid As2S3(s) + NO3-(aq) → H3AsO4(aq) + S(s) + NO(g) Is this the correct balanced equation? 32 H2O + 24 As2S3(s) + 80 H+(aq...
June 21, 2013

Chemistry
Sorry, for the oxidizing, I put this: Fe^2+
June 21, 2013

Chemistry
Balance each of the following skeletal equations by using oxidation and reduction half reactions. All the reactions take place in acidic solution. Identify the oxidizing agent and reducing agent in each reaction. (Use the lowest possible coefficients. Include states-of-matter ...
June 21, 2013

Physics (trig)
The height of an outdoor basketball backboard is 12 1/3 feet and the backboard casts a shadow 19 1/5 feet. Find the angle of elevation of the sun (answer in units of degrees). Can someone help me with the formula? Thank you!
June 19, 2013

Physics (algebra)
the sonar of a navy cruiser detects a submarine that is d=4601 ft from the cruiser. the angle between the water level and the submarine is 0=32 degrees. What formula should I use to solve?
June 18, 2013

maths
a sum of money trebles in 9years 4 months.in how many years will it double
June 15, 2013

Chemistry
The pH of 0.40 M HF(aq) is 1.93. Calculate the change in pH when 0.301 g of sodium fluoride is added to 53.7 mL of the solution. Ignore any change in volume.
June 14, 2013

chemistry
Suppose that 0.483 g of an unknown monoprotic weak acid, HA, is dissolved in water. Titration of the solution with 0.250 M NaOH(aq) required 42.0 mL to reach the stoichiometric point. After the addition of 21.0 mL, the pH of the solution was found to be 3.75. (a) What is the ...
June 14, 2013

Chemistry
moles of H2SO3 = 0.0246 moles of 2NaOH = 0.04925 Second stiochiometric point volume: 400. mL First stiochiometric point volume: 200. mL Thanks!
June 14, 2013

Chemistry
What volume of 0.123 M NaOH(aq) must be added to 125 mL of 0.197 M H2SO3(aq) to reach the following points? (a) the first stoichiometric point (b) the second stoichiometric point
June 14, 2013

Chemistry
What volume of 0.123 M NaOH(aq) must be added to 125 mL of 0.197 M H2SO3(aq) to reach the following points? (a) the first stoichiometric point (b) the second stoichiometric point
June 14, 2013

CALCULUS
Find the gradient and directional derivative of f at P in the direction of v: f(x,y)=ln(x^2 + y^2 +1)+ e^(2xy) P(0,2) v=5i-12j
June 2, 2013

Calculus - HELP plz!
Find all of the first partial derivatives of f(x,y,z)=arctan y/xz
June 2, 2013

vectors
why are the answers in the back of my textbook,[3,4,-1], [4,5,-5], [2,3,3]
May 27, 2013

vectors
find three points on each plane [x,y,z]= [3,4,-1]+s[1,1,-4]+ t[2,-5,3]
May 27, 2013

physics
a horizontal force of 600Npulls two masses 10kg lying on a frictionnnnless surface connected by a light string .what is the tension in the string?Does the answer depend on which mass end the pull is applied
May 26, 2013

physics
explai biot-savart,law.an electron with velocity 3*107ms1 describe a circular path in a uniform magnetic field of 0.2T,perpendicular to it.calculate the radius of path
May 23, 2013

math
at a certain factory each worker either drives to work or take the bus. the ratio of worker who take the bus to those who drive to work is 2:5. if 120 worker drive to work how many workers are there at the factory?
May 16, 2013

Physical Science
my dear , how did you get this formula of KE, KE=mv2/2 and the mass is equal to (rho)(volume ) so KE=(RHO)(VOLUME)(V2)/2 ,, I confused , can you explain more please
May 13, 2013

Physical Science
Thank you
May 13, 2013

Physical Science
- What is the kinetic energy ,KE, per unit volume V of blood that has a speed of 0.5 m/s. Take density ofƒâblood = 1.0x103kg/m3
May 13, 2013

Microbiology
How can lab practices and safety precautions help reduce hazards in a lab setting? How do you handle blood cultures and pathogenic strains in a lab to minimize contamination?
May 3, 2013

maths
Consider the following system of inequalities: {(c−1)x^2+2cx+c+4≤0 cx^2+2(c+1)x+(c+1)≥0 The sum of all real values of c, such that the system has a unique solution, can be written as ab, where a and b are coprime positive integers. What is the value of a+b? ...
May 3, 2013

statistics
the probability that a house in an urban area will develop a leak is 5%. if 23 houses are randomly selected, what is the probability that none of the houses will develop a leak?
April 28, 2013

Chemistry
What is the pH of a solution of 40.0 ml of 0.800 M HCl titrated with 4.00 ml of 1.00 M Hydroxyl amine?
April 24, 2013

thanxxxxxxx hero.........
April 23, 2013

chemistry
how many gram of h2 needed to react with 3.10 n2
April 18, 2013

chemistry
how many gram of h2 needed to react with 3.10 n2
April 18, 2013

PHYSICS
The only force acting on a particle is conservative force F. If the particle is at point A, the potential energy of the system associated with F and the particle is 39 J. If the particle moves from point A to point B, the work done on the particle by F is +25 J. What is the ...
April 17, 2013

CALCULUS-plz help!
For the curve r = 2 sin 3(theta): Find the arc length of one petal
April 16, 2013

CALCULUS-plz help!
For the curve r = 2 sin 3(theta): Find the arc length of one petal
April 16, 2013

Math
I think I figure it out. The answer is: 12 A ^2 * 2 A * - 31 + 4 A * 6 + / I figured that that the square sign and the number 2 count as one operator. For ^2 I just use the x^2 button on the calculator and it gave me the same answers.
April 15, 2013

Math
I need to change this expression to postfix form. (12*A^2-2*A+31)/(4*A+6) I know how to do this except for the squaring part. I got stuck. This is my try. 12 A 2 ^ * 2 A * - 31 + 4 A * 6 + / When I test this in a calculator, it gives different results. Another problem is that ...
April 15, 2013

biology
i am researching an article and am having trouble understanding the title. can someone please explain to me in simple terms: Deficiency of a Beta-arrestin-2 signal complex contributes to insulin resistance. so what is a beta arrestin 2 signal complex?
April 15, 2013

Chemistry
radioactive sodium chloride is appropriate for diagnosing circulatory problems, but radioactive xenon is helpful in searching for lung problems. Explain why. I understand different elements are used for specific parts of the body but I don't understand this question. ...
April 14, 2013

physics
A 22.0 Ω, 11.0 Ω, and 6.00 Ω resistor are connected in parallel to an emf source. A current of 6.00 A is in the 11.0 Ω resistor.What is the potential diﬀerence across the source? Answer in units of V
April 14, 2013

commerce
April 14, 2013

physics
An 8.0 Ω resistor and a 4.0 Ω resistor are connected in series with a battery. The potential diﬀerence across the 4.0 Ω resistor is measured as 9 V. Find the potential diﬀerence across the battery.
April 14, 2013

chemistry
A solution of household bleach contains 5.25% sodium hypochlorite, NaOCl, by mass. Assuming that the density of bleach is the same as water, calculate the volume of household bleach that should be diluted with water to make 500.0 mL of a pH = 10.23 solution.
April 10, 2013

chemistry
The Ka of a monoprotic weak acid is 7.25 × 10-3. What is the percent ionization of a 0.167 M solution of this acid? If the concentration is more than 1000 times greater than the Ka, then you can make an assumption that simplifies the algebra needed to solve the problem. ...
April 10, 2013

chemistry
The half-equivalence point of a titration occurs half way to the end point, where half of the analyte has reacted to form its conjugate, and the other half still remains unreacted. If 0.460 moles of a monoprotic weak acid (Ka = 3.8 × 10-5) is titrated with NaOH, what is ...
April 10, 2013

chemistry
A flask contains 0.342 g of acid and a few drops of phenolphthalein indicator dissolved in water. The buret contains 0.120 M NaOH. 20.f mL of base is needed to reach the endpoint of the titration. Assuming that the acid is monoprotic, what is the molar mass?
April 10, 2013

childhood edu
One of Rudolph Dreikur's contributions to the field of early childhood education is his belief that? A. All behavior is goal directed. B.There's a difference between behavior and misbehavior I think it's A,am I correct
April 9, 2013

math
solve the problem A drug is injected into a patient and the concentration of the drug is monitored. The drug's concentration, C(t), in milligrams after t hours is modeled by C(t) = (7t)/2t^2+4.
April 7, 2013

epidemiology
Let’s say you are a health policy expert and you are sitting in your office and you receive a phone call from a news reporter. The reporter asks you to comment for a story she is writing. She has learned from the chief of neurosurgery at Cooper University Hospital that ...
April 5, 2013

epidemiology
In a study examining associations between level of education and response to the Philadelphia Public Health Department’s emergency messages to “shelter in place” (meaning stay in your home) following an accidental release of chemicals from the Sunoco refinery in...
April 5, 2013

epidemiology
) In a recently published article authors reported on their research examining the effectiveness of compound C-4277, an anti-viral agent. This agent was tested to determine its impact on rhinoviruses, which are the leading cause of common colds. The article states that 1,800 ...
April 5, 2013

chemistry
I mean the head temp. is the higher temp., they called it like this in my university. anyway,this question in the dehydration of cyclohexanol. when we do elimination the heat temp. should be kept below 90 c, why?
March 30, 2013

chemistry
why is the head temperature kept below 90 c in the initial step of the dehydration reaction?
March 30, 2013

Calculus-PLZ HELP! =)
does the sum 3/(2^(n)-1) converge or diverge? n=1--->infinity
March 26, 2013

Calculus II
Is the series 1/(n(n+1)) convergent? n=2 to n=infinity
March 25, 2013

Calculus II
Does 3/(2^(n) +1) diverge or converge in an infinite sum?
March 25, 2013

Chemistry
Nvm figured it out
March 22, 2013

Chemistry
Why is the last step is convert to pH? We are trying to find the hydroxide-ion concentration?not the pH
March 22, 2013

Chemistry
what is the hydronium-ion concentration in a 0.35m solution of NaCO3? For carbonic acid, Ka1=4.2x10^-7 and Ka2=4.8x10^-11. (Kw=1.0x10^-14)
March 22, 2013

Chemistry
I don't press the E button i press the 10^x Button but when I divided the kw/Kb it gives me 2.083x10^-28
March 22, 2013

Chemistry
I plug in the numbers put it doesn't match any of the choices.... I get 4.81x10^-29 The choices are A)2.3x10^-35 B)6.4x10^-23 C)7.3x10^-16 D)48 E)491 Please help!!
March 22, 2013

Chemistry
What is Kc for the following equilibrium? For phosphoric acid, Ka1=6.9x10^-3, Ka2=6.2x10^-8 and Ka3=4.8x10^-13 HPO4^-2 + OH^- <==> PO4^-3 + H2O
March 22, 2013

physics
Calculate the magnitude of the gravitational force between the Earth and an m = 6.00 kg mass on the surface of the Earth. The distance to the center of the Earth from the surface is 6.37×103 km and the mass of the Earth is 5.98×1024 kg. B)Calculate the magnitude of...
March 22, 2013

english
complete the sentence please! a kite___ tries to catch a falling kite before it lands.
March 21, 2013

chemistry
How many mL of 0.40M NaOH are need to neutralize 30.0 mL of 0.50 M H2SO4 according to the following reaction. 2NaOH(aq) + H2SO4 (aq)----Na2SO4 (aq) + 2H2O(l)
March 20, 2013

English
Which senses are appealed to in these lines from Macbeth? Nay, had I pow'r, I should / Pour the sweet milk of concord into hell, / Uproar the universal peace… A. smell, taste, and touch B. hearing, sight, and smell C. sight, taste, and hearing D. hearing, taste, and ...
March 20, 2013

Childhood
Thanks :)))
March 19, 2013

Childhood
Two most common aspects of malnutrition in the u.s are: a) heart disease and obesity b) iron deficiency and heart disease c) dental decay and iron deficiency d) obesity and dental decay. I chose c) dental and iron deficiency is that right?
March 19, 2013

curriculum development
I'm using notes and Internet not text, I can't find much info
March 19, 2013

Childhood
The fundamental purpose of early childhood education should be to a) prepare children for continuing later success in elementary school. B) foster growth of developmental sequences c) foster competence in dealing with life .is letter c) correct?
March 19, 2013

Chemistry
I could use some help please. Ammmonia, NH3, can be made by reacting Nitrogen with Hydrogen. N2+3H2=2NH3 How many moles of NH3 can be made if 7.5 moles of H2 react eith enough N2? Thank-you in advance for any help
March 18, 2013

College algebra
Find the value of f(x) = -3x^2 + 12x-8
March 15, 2013

Find the following inequality
Find the following inequality. 15(x^2-1)>16x
March 15, 2013

accounting
13. A drawback to using _______ when inventory costs are rising is that the company reports lower net income. A. LIFO B. FIFO C. specific-identification costing D. average costing 14. The balance sheet format that lists assets
March 12, 2013

Math
what is a model that shows 180 divided by 9
March 11, 2013

MATH
There is a slide in the park that is 18 feet long. The ladder to the top of the slide is 7.5 feet long. If the ladder and the slide are perpendicular, what is "D", the distance from the top of the slide to the ground? Explain how you got your answer.
March 10, 2013

math
There is a slide in the park that is 18 feet long. The ladder to the top of the slide is 7.5 feet long. If the ladder and the slide are perpendicular, what is "D", the distance from the top of the slide to the ground? Explain how you got your answer.
March 10, 2013

math
2x+3y=13 5x+2y=16
March 10, 2013

Math
If you have 36ft of fencing what are the areas of the different rectangles you could enclose with the fencing? Consider only whole number dimensions.
March 7, 2013

chem
Calculate the pH of a solution made by adding 3.20 g of lithium oxide (Li2O) to enough water to make 1.210 L of solution. (Kw = 1.0 10-14)
March 7, 2013

chemistry
i did what you told me to and had to use the quadratic and got 1.430e-6 for the OH- but it was wrong. is that what you got?
March 6, 2013

chemistry
Calculate the hydronium ion concentration and pH in a 0.037 M solution of sodium formate, NaHCO2. hydronium ion concentration i dont understand these
March 6, 2013

chem
select the stronger base. how do i know this? 1.SeO42− or SO42− 2.BrO− or BrO2−
March 6, 2013

physics
Jacob found a piece of a broken glass bottle. He picked it up and made these observations about it: 1. No color (clear) 2. Makes scratches on wood 3. Has a bumpy surface 4. Broke when I dropped it He thinks the glass is a solid and most of his observations could only apply to ...
March 5, 2013

physics
Jacob found a piece of a broken glass bottle. He picked it up and made these observations about it: 1. No color (clear) 2. Makes scratches on wood 3. Has a bumpy surface 4. Broke when I dropped it He thinks the glass is a solid and most of his observations could only apply to ...
March 5, 2013

Physics
A 1200.0-kg car speeds up from 16.0 m/s to 20.0 m/s. How much work was done on the car to increase its speed?
March 5, 2013

chemistry
Calculate the molar concentration of OH− ions in an 1.79 M solution of hypobromite ion (BrO−; Kb = 4.0 10-6).
March 4, 2013

Math...I think...
A building casts a shadow 54 feet long at the same time a 6 foot tall man casts a shadow 4 feet long. How tall is the tree?
March 1, 2013

Finance
CAN SOMEONE PLEASE PLEASE HELP ME WITH A FINANCE QUESTION THAT I POSTED YESTERDAY,WEDNESDAY,FEB 27TH @ 5:58PM.PLAEASE,ANY AND ALL HELP WILL BE GREATLY APPRECIATED
February 28, 2013

physics
a chinook salmon
February 28, 2013

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